US4897371A - Glass article protected from coloring by electron rays and method of using - Google Patents
Glass article protected from coloring by electron rays and method of using Download PDFInfo
- Publication number
- US4897371A US4897371A US07/146,449 US14644988A US4897371A US 4897371 A US4897371 A US 4897371A US 14644988 A US14644988 A US 14644988A US 4897371 A US4897371 A US 4897371A
- Authority
- US
- United States
- Prior art keywords
- glass
- weight
- ions
- electron rays
- glass article
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C21/00—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
- C03C21/001—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions
- C03C21/002—Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface in liquid phase, e.g. molten salts, solutions to perform ion-exchange between alkali ions
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/083—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound
- C03C3/085—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal
- C03C3/087—Glass compositions containing silica with 40% to 90% silica, by weight containing aluminium oxide or an iron compound containing an oxide of a divalent metal containing calcium oxide, e.g. common sheet or container glass
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/86—Vessels; Containers; Vacuum locks
- H01J29/863—Vessels or containers characterised by the material thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/24—Manufacture or joining of vessels, leading-in conductors or bases
- H01J9/244—Manufacture or joining of vessels, leading-in conductors or bases specially adapted for cathode ray tubes
Definitions
- the present invention relates to a glass article protected from coloring by electron rays which is suitable for use as the glass panel of a cathode ray tube (CRT for short hereinafter) which is irradiated with electron rays, and also to a process for producing the same.
- CRT cathode ray tube
- the glass panel of a CRT is subject to coloring (referred to as browning hereinafter) by bombardment with electron rays.
- browning referred to as browning hereinafter
- the glass panel is produced from glass of specific composition containing Sr, Ba, Ce, etc.
- the production process includes melting the glass, feeding the gob to the mold, pressing the gob, and grinding the glass panel.
- the conventional glass panel is required to have a considerable thickness so that it withstands a pressure higher than 3 kg.f/cm 2 (29.4 N/cm 2 ). This leads to an increase in weight.
- the present invention includes the following seven aspects.
- a process for producing said glass article which comprises contacting a soda-lime-silica glass with a molten salt containing lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions at 430° to 490° C. for 0.5 to 4 hours.
- a process for producing said glass article which comprises contacting a glass molding of said composition with a molten salt containing potassium ions at 430° to 490° C.
- a process for producing a glass article protected from coloring by irradiation with electron rays which comprises contacting a soda-lime-silica glass molding with a molten salt containing potassium ions and at least one kind of calcium ions, barium ions, and strontium ions so that the surface layer of the glass molding has a composition defined by a molar ratio of 0.4 to 0.65 for Na 2 O/(Na 2 O+K 2 O), said surface layer having a depth to which the irradiated electrons penetrate. (This depth is referred to as the maximum range hereinafter.)
- a process for producing a glass article which comprises contacting a soda-lime-silica glass with a molten salt containing potassium ions and lithium ions and subsequently subjecting the glass to heat treatment so that the surface layer from the surface to the maximum range has a composition defined by a molar ratio of 0.4 to 0.65 for Na 2 O/(Na 2 O+K 2 O) and by a molar ratio of 0.05 to 0.3 for Li 2 O/(total amount of alkali-metal oxides).
- a process for producing a glass article which comprises contacting a soda-lime silica glass with a molten salt containing potassium ions and subsequently subjecting the glass to heat treatment so that the surface layer from the surface to the maximum range has a composition defined by a molar ratio of 0.4 to 0.65 for Na 2 O/(Na 2 O+K 2 O).
- FIG. 1 is a sectional view of a CRT glass panel pertaining to one embodiment of the present invention.
- FIG. 2 is a graph showing the molar ratio of Na 2 O/(Na 2 O+K 2 O) in the surface layer of the glass panel. (The solid line indicates the data in Example 7 and the broken line indicates the data in Comparative Example 5.)
- FIG. 3 is a graph showing the molar ratio of Na 2 O/(Na 2 O+K 2 O) in the surface layer of the glass panel. (The solid line indicates the data in Example 8 and the broken line indicates the data Comparative Example 6.)
- FIG. 4 is a graph showing the molar ratio of Li 2 O/(Li 2 O+Na 2 O+K 2 O) in the surface layer of the glass panel of Example 8.
- the glass article pertaining to the first aspect of the present invention is a molded glass plate of commercial soda-lime-silica glass, with the surface thereof, which is irradiated with electron rays, modified so that sodium ions therein are exchanged by lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions.
- the partial exchange of sodium ions with lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions produces the "mixed alkali effect", which makes the glass plate less liable to browning by irradiation with electron rays and forms a compressed layer in the glass surface, leading to increased glass strength.
- Lithium ions exchanged with the sodium ions are present in the form of lithium oxide in the glass.
- the average content of lithium oxide should preferably be 0.1 ⁇ 3 wt % in a depth of 10 ⁇ m to which electron rays penetrate from the irradiated surface. With an average content of lithium oxide in excess of 3 wt %, the glass molding has a low strength and, in an extreme case, has a turbid surface and fine surface cracks.
- the exchange of sodium ions by potassium ions, rubidium ions, and cesium ions should preferably take place in a depth of 5 to 20 ⁇ m from the surface.
- the exchange in an excessively shallow or deep layer does not produce the effect of preventing browning.
- the soda-lime-silica glass molding is one which is produced by float process. It has a composition of SiO 2 69 ⁇ 73%, Al 2 O 3 0.5 ⁇ 1.5%, Fe 2 O 3 0 ⁇ 0.15%, CaO 7 ⁇ 14%, MgO 0 ⁇ 4.5%, Na 2 O 12 ⁇ 16%, K 2 O 0-1.5%, TiO 2 0 ⁇ 0.1%, and SO 3 0 ⁇ 0.5% by weight. Moreover, it is desirable that the surface of the glass molding which is irradiated with electron rays is opposite to the side which comes into contact with molten tin in the float bath. Otherwise, the surface of the molding is slow to undergo the ion exchange and the tin present on the glass surface tends to cause browning.
- the glass article pertaining to the first aspect of the present invention is produced by the process pertaining to the second aspect of the present invention.
- a CRT glass plate of desired shape is formed from soda-lime-silica glass and the resulting molding is dipped in a molten salt containing lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions at 430° to 490° C. for 0.5 to 4 hours, so that sodium ions in the surface of the glass molding are exchanged by lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions.
- the amount of lithium ions in the molten salt bath based on the total amount of at least one kind of potassium ions, rubidium ions, and cesium ions should preferably be 0.04 ⁇ 0.4 mol %. If the amount of lithium ions is higher than 0.4 mol %, the resulting glass article has a low strength and, in an extreme case, has a turbid surface and fine surface cracks.
- the glass molding is produced by forming a glass plate, it is possible to keep the glass surface flat without grinding and polishing it.
- the glass article pertaining to the first aspect of the present invention is characterized by that the surface thereof is treated so that sodium ions therein are partly exchanged by lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions.
- the thus treated glass surface is very little subject to browning when irradiated with electron rays. This leads to an advantage that a commercial soda-lime-silica glass plate can be used as a raw material for the CRT glass panel, and that the glass panel can be produced without a grinding and polishing step and hence at a low cost.
- the glass panel produced according to the present invention has an increased strength and hence it outperforms the conventional one with a smaller thickness, because the glass surface has a compressed surface layer which is formed by the partial exchange of sodium ions in the surface layer by at least one kind of potassium ions, rubidium ions, and cesium ions.
- the glass article pertaining to the third aspect of the present invention is characterized by that the surface thereof which is irradiated with electron rays is modified so that sodium ions are exchanged by potassium ions. It is made from a glass plate composed of SiO 2 69 ⁇ 73%, Al 2 O 3 0.5 ⁇ 1.5%, Fe 2 O 3 0 ⁇ 0.15%, CaO 7 ⁇ 14%, MgO 0 ⁇ 4.5%, Na 2 O 12 ⁇ 16%, K 2 O 0 ⁇ 1.5%, TiO 2 0 ⁇ 0.1%, SO 3 0 ⁇ 0.5%, and Li 2 0.2 ⁇ 1.5% by weight.
- the third aspect of the present invention is based on the following knowledge.
- the browning caused by electron rays takes place because alkali ions in the outermost layer of glass move inward when the glass is irradiated with electron rays and they change into metallic alkali atoms in a depth of 0.5 ⁇ 8 ⁇ m from the surface. It is known that when there are two or more kinds of alkalis in glass, they prevent browning owing to the mixed alkali effect. Moreover, browning can be prevented more effectively when 0.2 ⁇ 1.5 wt % of Li 2 O is added in addition to Na 2 O and K 2 O. If the amount of Li 2 O is less than 0.2 wt %, browning is not effectively prevented.
- the weight ratio of Na 2 O/(Na 2 O+K 2 O) should be 0.2 ⁇ 0.6. Outside this range, the effect of preventing browning is little.
- the depth of the layer in which coloring takes place by irradiation with electron rays is determined by the distance to which electron rays penetrate. The depth is expressed by the following formula. (Thomson - Widington Law)
- D (cm) is a depth in glass to which electron rays penetrate
- V (volt) is an accelerating voltage of electron rays
- d(g/cm 3 ) is a density of glass
- ⁇ is a constant 6.2 ⁇ 10 11 volt 2 .cm 2 /g.
- the accelerating voltage V (volt) of electron rays is 10 kV, 20 kV, and 30 kV
- the electron rays will penetrate to a depth of 0.62 ⁇ m, 2.48 ⁇ m, and 5.58 ⁇ m, respectively.
- Electron ray was found experimentally to penetrate to a depth of 0.5 to 1.5 ⁇ m, 0.75 to 4 ⁇ m and 2.0 to 6.5 respectively when the electron ray was irradiated on a surface of soda-lime-silica glass under an accelerating voltage of 10 kV, 20 kV and 30 kV.
- the glass molding pertaining to the third aspect of the present invention should have the composition defined as follows:
- the content of Li 2 O in the surface layer deeper than 0.5 ⁇ m is 0.2 ⁇ 1.5 wt %, with the ratio of Na 2 O/(Na 2 O+K 2 O) being 0.2 ⁇ 0.6.
- a glass article like this is produced by the process pertaining to the fourth aspect of the invention.
- a glass plate composed of SiO 2 69 ⁇ 73%, Al 2 O 3 0.5 ⁇ 1.5%, Fe 2 O 3 0 ⁇ 0.15%, CaO 7 ⁇ 14%, MgO 0 ⁇ 4.5%, Na 2 O 12 ⁇ 16%, K 2 O 0 ⁇ 1.5%, TiO 2 0 ⁇ 0.1%, SO 3 0 ⁇ 0.5%, and Li 2 O 0.2 ⁇ 1.5% by weight, is formed into a desired shape and the glass plate is dipped in a molten salt bath containing potassium ions at 430° to 490° C. for a prescribed period of time, so that sodium ions in the surface layer are partly exchanged by potassium ions.
- An advantage of the ion exchange process is that it is possible to control the depth of the surface layer in which the ion exchange takes place by adjusting the period of time during which the glass panel is dipped in the molten salt bath.
- the dipping time for ion exchange may be properly established according to the accelerating voltage of a CRT.
- the above-mentioned glass composition (SiO 2 69 ⁇ 73%, Al 2 O 3 0.5 ⁇ 1.5%, Fe 2 O 3 0 ⁇ 0.15%, CaO 7 ⁇ 14%, MgO 0 ⁇ 4.5%, Na 2 O 12 ⁇ 16%, K 2 O 0 ⁇ 1.5%, TiO 2 0 ⁇ 0.1%, SO 3 0 ⁇ 0.5%, and Li 2 O 0.2 ⁇ 1.5% by weight) can be obtained using a furnace for the production of soda-lime-silica glass. Therefore, glass article of the present invention can be produced without using a special furnace. This is advantageous in production cost. In addition, if the glass article of the present invention is produced from a glass plate made by float process, it has a smooth surface and needs no polishing after molding.
- the glass strength can decrease on account of the exchange of sodium by lithium. This makes it necessary to increase the thickness of the glass plate where the glass plate is used as a vacuum container such as a CRT. Increasing the thickness is disadvantageous in production cost and weight reduction of CRTs.
- the glass article pertaining to the third and fourth aspects of the present invention has an advantage over the conventional one.
- the partial exchange of sodium ions by potassium ions renders the glass panel resistant to browning by electron rays on account of the mixed alkali effect. Moreover, it forms a compressed layer of the glass surface and thereby increases the glass strength.
- the glass article pertaining to the fourth aspect of the present invention is made of a glass plate composed of SiO 2 69 ⁇ 73%, Al 2 O 3 0.5 ⁇ 1.5%, Fe 2 O 3 0 ⁇ 0.15%, CaO 7 ⁇ 14%, MgO 0 ⁇ 4.5%, Na 2 O 12 ⁇ 16%, K 2 O 0 ⁇ 1.5%, TiO 2 0 ⁇ 0.1%, SO 3 0 ⁇ 0.5%, and Li 2 O 0.2 ⁇ 1.5% by weight, with the surface thereof modified such that sodium ions therein are partly exchanged by potassium ions. Therefore, it is very little subject to browning when irradiated with electron rays.
- the glass article of the present invention is produced from a glass plate made by float process, it has a smooth surface and needs no polishing after molding.
- the fifth aspect of the present invention is concerned with a process for producing a glass article protected from coloring by electron rays.
- a glass molding formed from soda-lime-silica glass is dipped in a molten salt bath containing potassium ions and at least one kind of calcium ions, barium ions, and strontium ions, so that sodium ions in the surface layer thereof are partly exchanged by potassium ions.
- the ion exchange is accomplished to such an extent that the molar ratio of Na 2 O/(Na 2 O+K 2 O) becomes 0.4 ⁇ 0.65 in the surface layer to the depth of maximum range from the surface.
- the depth in glass (maximum range) to which electron rays penetrate is determined by the accelerating voltage of electron rays, and it is known that the depth can be expressed by the formula
- D (cm) is a depth in glass to which electron rays penetrate
- V (volt) is an accelerating voltage of electron rays
- d (g/cm 3 ) is a density of glass
- ⁇ is a constant 6.2 ⁇ 10 11 volt 2 .cm 2 /g.
- the accelerating voltage V (volt) of electron rays is 10 kV, 20 kV, and 30 kV
- the electron rays will penetrate to a depth of 0.62 ⁇ m, 2.48 ⁇ m, and 5.58 ⁇ m, respectively.
- Electron ray was found experimentally to penetrate to a depth of 0.5 to 1.5 ⁇ m, 0.75 to 4 ⁇ m and 2.0 to 6.5 ⁇ m respectively when the electron ray was irradiated on a surface of sodium-lime-silica glass under an accelerating voltage of 10 kV, 20 kV and 30 kV.
- the period of time for treatment in a molten salt bath should be determined in proportion to the anticipated accelerating voltage of electron rays or the maximum range. Thus it is necessary to carry out the treatment with a salt containing potassium ions and strontium ions, etc. so that the surface layer within the maximum range has a composition defined by the molar ratio of Na 2 O to the total amount of Na 2 O and K 2 O which is 0.4 ⁇ 0.65.
- the molten salt used for the treatment of soda-lime-silica glass should contain 99.90 ⁇ 99.99 mol % of a salt containing potassium ions.
- the treatment with the molten salt should preferably be performed at 440° to 480° C. for 0.5 to 4 hours.
- the sixth aspect of the present invention is concerned with a process for producing a glass article protected from coloring by electron rays.
- a glass molding formed from soda-lime-silica glass is dipped in a molten salt bath containing potassium ions and lithium ions, so that sodium ions in the surface layer of the glass molding are exchanged by potassium ions and lithium ions.
- the treated glass article further undergoes heat treatment.
- the heat treatment may be performed when the article is in a heating process (such as a sealing or baking process) during an assembling process of a CRT.
- the treatment process may be performed itself.
- the ion exchange is accomplished to such an extent that the molar ratio of Na 2 O/(Na 2 O+K 2 O) becomes 0.4 ⁇ 0.65 and that the molar ratio of Li 2 O/(total amount of alkalimetal oxides) becomes 0.05 ⁇ 0.3 in the surface layer almost to the depth of maximum range from the surface.
- the surface layer of the soda-lime-silica glass undergoes change in composition. That is, 70 ⁇ 100% of sodium ions in the surface layer is exchanged by potassium ions and lithium ions.
- the subsequent heat treatment causes sodium ions and potassium ions to diffuse to the depth of maximum range from the surface.
- the composition in the surface layer of that depth has a composition defined by the molar ratio of Na 2 O to the total amount of Na 2 O and 220 which is 0.4 ⁇ 0.65 and by the molar ratio of Li 2 O to the total amount of alkali-metal oxides which is 0.05 ⁇ 0.3.
- the depth in glass (maximum range) to which electron rays penetrate is determined by the accelerating voltage of electron rays.
- the electron rays will penetrate to a depth of 2.5 ⁇ m, 4.5 ⁇ m, and 7.5 ⁇ m, respectively. Electron ray was found experimentally to penetrate to a depth of 0.5 to 1.5 ⁇ m, 0.75 to 4 ⁇ m and 2.0 to 6.5 ⁇ m respectively when the electron ray was irradiated on a surface of soda-lime-silica glass under an accelerating voltage of 10 kV, 20 kV and 30 kV.
- the adequate temperature and time for the treatment should be established according to the anticipated accelerating voltage of electron rays and the conditions of ion exchange, so that the molar ratio of Na 2 O to the total amount of Na 2 O and K 2 O becomes 0.4 ⁇ 0.65.
- the ion exchange and heat treatment require a higher temperature and a longer time as the anticipated accelerating voltage of electron rays increases.
- potassium nitrate and lithium nitrate are used as the molten salt containing potassium ions and lithium ions.
- the molten salt should preferably be kept at 440° to 480° C. and the dipping time should preferably be 0.5 to 4 hours.
- the heat treatment should be performed at 440° to 480° C. for 1 to 10 hours.
- the seventh aspect of the present invention is concerned with a process for producing a glass article protected from coloring by electron rays.
- a glass molding formed from soda-lime-silica glass is dipped in a molten salt bath containing potassium ions, so that sodium ions in the surface layer of the glass molding are exchanged by potassium ions.
- the treated glass article further undergoes heat treatment.
- the ion exchange is accomplished to such an extent that the molar ratio of Na 2 O/(Na 2 O+K 2 O) becomes 0.4 ⁇ 0.65 wt in the surface layer to the depth of maximum range from the surface.
- the surface layer of the soda-lime-silica glass undergoes change in composition. That is, 70 ⁇ 80% of sodium ions in the surface layer is exchanged by potassium ions, and the surface layer contains both sodium ions and potassium ions.
- the subsequent heat treatment causes sodium ions and potassium ions to diffuse to the depth of maximum range from the surface.
- the composition in the surface layer of that depth has a composition defined by the molar ratio of Na 2 O to the total amount of Na 2 O and K 2 O which is 0.4 ⁇ 0.65 wt.
- the depth in glass (maximum range) to which electron rays penetrate is determined by the accelerating voltage of electron rays as expressed by the formula
- the accelerating voltage V (volt) of electron rays is 10 kV, 20 kV, and 30 kV, the electron rays will penetrate to a depth of 0.62 ⁇ m, 2.48 ⁇ m, and 5.58 ⁇ m, respectively.
- the adequate temperature and time for the treatment should be established according to the anticipated accelerating voltage of electron rays and the conditions of ion exchange, so that the molar ratio of Na 2 O to the total amount of Na 2 O and K 2 O becomes 0.4 ⁇ 0.65 wt.
- the ion exchange and heat treatment require a higher temperature and a longer time as the anticipated accelerating voltage of electron rays increases.
- potassium nitrate is used as the molten salt containing potassium ions.
- the molten salt should preferably be kept at 440° to 480° C. and the dipping time should preferably be 0.5 to 4 hours, and the heat treatment should be performed at 440° to 480° C. for 1 to 10 hours.
- soda-lime-silica glass is used.
- the preferred composition of the glass is shown in Table 1.
- the glass used in the fifth, sixth and seventh aspects of the present invention should have such a composition that the alkali metal oxide accounts for 5 wt % and more, preferably 10 wt % and more, in the glass and sodium oxide accounts for 65 wt % and more, preferably 80 wt % and more, in the alkali metal oxide. With a composition outside this range, the glass article is poor in resistance to coloring by electron rays.
- the surface layer of the glass up to a depth of the maximum range is modifies such that the molar ratio of Na 2 O to the total amount of Na 2 O and K 2 O is 0.4 ⁇ 0.65.
- the sodium ions and potassium ions present together in the surface layer are less mobile in the glass and hence less liable to form the colloids of alkali-metal atoms. For this reason, the glass article of the present invention is protected from coloring by electron rays.
- the glass article diminishes to discolor further than when two kinds of alkali ions present together therein.
- the present invention it is not necessary to use glass of special composition containing a large amount of potassium oxide for the prevention of coloring by electron rays. Therefore, the production of the glass article of the present invention does not need a special furnace and an expensive raw material.
- the glass article of the present invention is superior in resistance to coloring by electron rays to the conventional glass for picture tubes of color television.
- a glass panel, 300 mm wide, 370 mm long, and 50 mm high, having a flat surface as shown in FIG. 1 was produced from a soda-lime-silica glass plate formed by float process, by heating and vacuum forming in combination with pressing. After pretreatment at about 200° C. for about 30 minutes, the glass panel was dipped in a molten salt bath composed of potassium nitrate and lithium nitrate at 460° C. for 2 hours. The content of lithium nitrate in the molten salt bath was 0 mol % in Comparative Example 1, 0.04 mol % in Example 1, 0.15 mol % in Example 2, and 0.4 mol % in Example 3. After dipping, the glass panel was washed.
- Table 2 shows the average concentration (wt %) of lithium oxide in the surface layer up to a depth of 10 ⁇ m from the surface of the glass panel. Table 2 also shows the molar ratio of Na 2 O/(Na 2 O+K 2 O) in the same surface layer.
- the glass panel obtained by the above-mentioned process was irradiated with electron rays for 300 hours using an electron gun (cathode voltage: 21 kV, cathode current: 300 ⁇ A, and surface current density: 1.00 ⁇ A/cm 2 ). After that, the glass panel was examined for light transmittance at a wavelength of 400 nm.
- the change of absorbance In (T 0 /T) is shown in Table 2. (T 0 and T stand for the transmittance of light before and after irradiation with electron rays.)
- a glass panel, 300 mm wide, 370 mm long, and 50 mm high, having a flat surface as shown in FIG. 1 was produced from a glass plate having the composition as shown in Table 3, by heating and vacuum forming in combination with pressing. After pretreatment at about 200° C. for about 30 minutes, the glass panel was dipped in a molten salt of potassium nitrate at 460° C. for 2 hours. After dipping, the glass panel was washed. For comparison (Comparative Example 3), the same glass panel was produced from glass for color TV picture tubes having the browning-resistant composition as shown in Table 4.
- Table 5 shows the ratio by weight of Na 2 O/(Na 2 O+K 2 O) in the same surface layer of the glass panel up to a depth of 2.5 ⁇ m from the surface.
- a test pieces cut out of the glass panel obtained by the above-mentioned process was irradiated with electron rays for 300 hours using an electron gun (cathode voltage: 20 kV, cathode current: 300 ⁇ A, and surface current density: 1.00 ⁇ A/cm 2 ). After that, the glass panel was examined for light transmittance at a wavelength of 400 nm.
- the change of absorbance In (T 0 /T) is shown in Table 5.
- T 0 and T stand for the transmittance of light before and after irradiation with electron rays.)
- the glass plate was irradiated with electron rays.
- the coloring caused by the irradiation was evaluated by measuring the change of transmittance.
- the ion exchange was carried out under the following conditions.
- the irradiation of electron rays was carried out under the following conditions.
- test piece was examined for transmittance of light with a wavelength of 400 nm.
- results are shown in Table 7.
- Comparative Example 4 the above-mentioned glass plate was treated with molten potassium nitrate at 460° C. for 1 hour and the treated glass plate was examined for light transmittance (400 nm) before and after irradiation with electron rays.
- Comparative Example 5 a commercial glass plate for color picture tubes was examined for light transmittance (400 nm) before and after irradiation with electron rays.
- Table 7 The molar ratio of Na 2 O/(Na 2 O+K 2 O) in the surface layer of the plate in Comparative Example 5 was measured. The results are shown in FIG. 2 (broken line). It is noted from Table 7 and FIG. 2 that the glass panel of the present invention decreases much less in transmittance after irradiation with electron rays than that in Comparative Examples 4 and 5.
- the glass plate was irradiated with electron rays.
- the coloring caused by the irradiation was evaluated by measuring the change of transmittance.
- the irradiation of electron rays was carried out under the following conditions.
- test piece was examined for transmittance of light with a wavelength of 400 nm.
- results are shown in Table 8.
- FIG. 3 solid line
- FIG. 4 shows the molar ratio of Li 2 O/(Li 2 O+Na 2 O+K 2 O) in the Example 8.
- Comparative Example 6 the above-mentioned glass plate underwent ion exchange but did not undergo heat treatment.
- Comparative Example 7 a commercial glass plate for color picture tubes had the composition as shown in Table 4. These glass plates in Comparative Example 6 and Comparative Example 7 were examined for light transmittance (400 nm) before and after irradiation with electron rays. The results are shown in Table 8. The molar ratio of Na 2 O/(Na 2 O+K 2 O) in the surface layer of the plate in Comparative Example 6 was measured. The results are shown in FIG. 3 (broken line). It is noted from Table 8 and FIG. 3 that the glass panel of the present invention decreases much less in transmittance after irradiation with electron rays than that in Comparative Examples 6 and 7.
- the glass plate was irradiated with electron rays.
- the coloring caused by the irradiation was evaluated by measuring the change of transmittance.
- the ion exchange was carried out under the following conditions.
- the irradiation of electron rays was carried out under the following conditions.
- test piece was examined for transmittance of light with a wavelength of 400 nm.
- results are shown in Table 9.
- Comparative Example 8 the above-mentioned glass underwent ion exchange but did not undergo heat treatment.
- Comparative Example 9 a commercial glass plate for color picture tubes had the composition as shown in Table 4. These glass plates in Comparative Example 8 and Comparative Example 9 were examined for light transmittance (400 nm) before and after irradiation with electron rays. The results are shown in Table 9. The molar ratio of Na 2 O/(Na 2 O+K 2 O) in the surface layer of the plate in Comparative Example 8 was measured. The results are almost same as shown in FIG. 3 (broken line). It is noted from Table 9 and FIG. 3 that the glass panel of the present invention decreases much less in transmittance after irradiation with electron rays than that in Comparative Examples 8 and 9.
Abstract
The instant invention relates to soda-lime-silica glass articles, having a surface which is resistant to coloring by electron rays which is suitable for use as the glass panel of a cathode ray tube. Said glass article being produced by a float process, and said surface having the sodium ions exchanged with lithium and at least one of potassium, rubidium, and cesium ions. In another aspect of the invention a soda-lime-silica glass containing 0.2-1.5% by weight of Li2 O having the sodium ions in at least one surface exchanged with potassiums is produced, such that the ratio of Na2 O/(Na2 O+K2 O) is 0.2-0.6 for a depth of 0.5 microns from said surface.
Description
The present invention relates to a glass article protected from coloring by electron rays which is suitable for use as the glass panel of a cathode ray tube (CRT for short hereinafter) which is irradiated with electron rays, and also to a process for producing the same.
The glass panel of a CRT is subject to coloring (referred to as browning hereinafter) by bombardment with electron rays. To remedy this trouble, the glass panel is produced from glass of specific composition containing Sr, Ba, Ce, etc. The production process includes melting the glass, feeding the gob to the mold, pressing the gob, and grinding the glass panel.
A disadvantage of this production process is that it needs a special furnace to melt the glass of specific composition and also needs the grinding step after press forming. These lead to a high production cost and low productivity.
Moreover, the conventional glass panel is required to have a considerable thickness so that it withstands a pressure higher than 3 kg.f/cm2 (29.4 N/cm2). This leads to an increase in weight.
On the other hand, it is possible to form the glass panel of a CRT from a soda-lime-silica glass plate. Unfortunately, this glass panel is subject to browning by irradiation with electron rays.
The coloring of soda-lime-silica glass by irradiation with electron rays is presumably induced by the following mechanism. Electrons impinging upon the glass plate penetrate into the surface layer of the glass plate in proportion to the accelerating voltage of electrons, and the electrons stay there and form electric field. This electric field causes sodium ions to move from the surface layer to the inner layer. These sodium ions form colloids composed of sodium-metal atoms in glass.
There is disclosed a process for producing glass protected from irradiation with electron rays in Japanese Patent Laid-open No. 105705/1975. This process is characterized by that lithium ions or sodium ions present in the surface layer of glass which is irradiated with electron rays are exchanged by at least one kind of potassium ions, rubidium ions, cesium ions, and hydrogen ions. However, this ion exchange process is not so effective in the prevention of browning.
There is proposed a method for preventing the coloring of glass by irradiation with electron rays in Japanese Patent Laid-open No. 153148/1987. According to this method, sodium ions in the surface layer of soda-lime-silica glass panel of a CRT which is irradiated with electron rays are exchanged by potassium ions. The ion exchange is accomplished by dipping a soda-lime-silica glass plate in potassium nitrate at 440° to 480° C. for 0.5 to 3 hours. As the result of ion exchange, the formation of colloids by sodium atoms diminishes. However, potassium ions moved from the surface layer to the inner layer form colloids composed of potassium atoms whereby the coloring of glass is diminished only a little.
It is an object of the present invention to provide a glass article which is very little subject to browning when it is irradiated with electron rays.
It is another object of the present invention to provide a glass article having a high strength.
It is further another object of the present invention to provide a process for producing said glass article at a low production cost.
The present invention includes the following seven aspects.
(1) A glass article molded from a soda-lime-silica glass molding, with the surface thereof modified so that sodium ions therein are exchanged by lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions.
(2) A process for producing said glass article which comprises contacting a soda-lime-silica glass with a molten salt containing lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions at 430° to 490° C. for 0.5 to 4 hours.
(3) A glass article produced from a glass molding composed of SiO2 69˜73%, Al2 O3 0.5˜1.5%, Fe2 O3 0˜0.15%, CaO 7˜14%, MgO 0˜4.5%, Na2 O 12˜16%, K2 O 0˜1.5%, TiO 2 0˜0.1%, SO3 0-0.5%, and Li2 O 0.2-1.5%, with the surface thereof modified so that sodium ions therein are exchanged by potassium ions.
(4) A process for producing said glass article which comprises contacting a glass molding of said composition with a molten salt containing potassium ions at 430° to 490° C.
(5) A process for producing a glass article protected from coloring by irradiation with electron rays which comprises contacting a soda-lime-silica glass molding with a molten salt containing potassium ions and at least one kind of calcium ions, barium ions, and strontium ions so that the surface layer of the glass molding has a composition defined by a molar ratio of 0.4 to 0.65 for Na2 O/(Na2 O+K2 O), said surface layer having a depth to which the irradiated electrons penetrate. (This depth is referred to as the maximum range hereinafter.)
(6) A process for producing a glass article which comprises contacting a soda-lime-silica glass with a molten salt containing potassium ions and lithium ions and subsequently subjecting the glass to heat treatment so that the surface layer from the surface to the maximum range has a composition defined by a molar ratio of 0.4 to 0.65 for Na2 O/(Na2 O+K2 O) and by a molar ratio of 0.05 to 0.3 for Li2 O/(total amount of alkali-metal oxides).
(7) A process for producing a glass article which comprises contacting a soda-lime silica glass with a molten salt containing potassium ions and subsequently subjecting the glass to heat treatment so that the surface layer from the surface to the maximum range has a composition defined by a molar ratio of 0.4 to 0.65 for Na2 O/(Na2 O+K2 O).
FIG. 1 is a sectional view of a CRT glass panel pertaining to one embodiment of the present invention.
FIG. 2 is a graph showing the molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the glass panel. (The solid line indicates the data in Example 7 and the broken line indicates the data in Comparative Example 5.)
FIG. 3 is a graph showing the molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the glass panel. (The solid line indicates the data in Example 8 and the broken line indicates the data Comparative Example 6.)
FIG. 4 is a graph showing the molar ratio of Li2 O/(Li2 O+Na2 O+K2 O) in the surface layer of the glass panel of Example 8.
The glass article pertaining to the first aspect of the present invention is a molded glass plate of commercial soda-lime-silica glass, with the surface thereof, which is irradiated with electron rays, modified so that sodium ions therein are exchanged by lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions.
The partial exchange of sodium ions with lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions produces the "mixed alkali effect", which makes the glass plate less liable to browning by irradiation with electron rays and forms a compressed layer in the glass surface, leading to increased glass strength.
Lithium ions exchanged with the sodium ions are present in the form of lithium oxide in the glass. The average content of lithium oxide should preferably be 0.1˜3 wt % in a depth of 10 μm to which electron rays penetrate from the irradiated surface. With an average content of lithium oxide in excess of 3 wt %, the glass molding has a low strength and, in an extreme case, has a turbid surface and fine surface cracks.
The exchange of sodium ions by potassium ions, rubidium ions, and cesium ions should preferably take place in a depth of 5 to 20 μm from the surface. The exchange in an excessively shallow or deep layer does not produce the effect of preventing browning.
The soda-lime-silica glass molding is one which is produced by float process. It has a composition of SiO2 69˜73%, Al2 O3 0.5˜1.5%, Fe2 O3 0˜0.15%, CaO 7˜14%, MgO 0˜4.5%, Na2 O 12˜16%, K2 O 0-1.5%, TiO 2 0˜0.1%, and SO 3 0˜0.5% by weight. Moreover, it is desirable that the surface of the glass molding which is irradiated with electron rays is opposite to the side which comes into contact with molten tin in the float bath. Otherwise, the surface of the molding is slow to undergo the ion exchange and the tin present on the glass surface tends to cause browning.
The glass article pertaining to the first aspect of the present invention is produced by the process pertaining to the second aspect of the present invention. According to the process, a CRT glass plate of desired shape is formed from soda-lime-silica glass and the resulting molding is dipped in a molten salt containing lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions at 430° to 490° C. for 0.5 to 4 hours, so that sodium ions in the surface of the glass molding are exchanged by lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions.
According to the process pertaining to the second aspect of the present invention, the amount of lithium ions in the molten salt bath based on the total amount of at least one kind of potassium ions, rubidium ions, and cesium ions should preferably be 0.04˜0.4 mol %. If the amount of lithium ions is higher than 0.4 mol %, the resulting glass article has a low strength and, in an extreme case, has a turbid surface and fine surface cracks.
In the case where the glass molding is produced by forming a glass plate, it is possible to keep the glass surface flat without grinding and polishing it.
The glass article pertaining to the first aspect of the present invention is characterized by that the surface thereof is treated so that sodium ions therein are partly exchanged by lithium ions and at least one kind of potassium ions, rubidium ions, and cesium ions. The thus treated glass surface is very little subject to browning when irradiated with electron rays. This leads to an advantage that a commercial soda-lime-silica glass plate can be used as a raw material for the CRT glass panel, and that the glass panel can be produced without a grinding and polishing step and hence at a low cost.
The glass panel produced according to the present invention has an increased strength and hence it outperforms the conventional one with a smaller thickness, because the glass surface has a compressed surface layer which is formed by the partial exchange of sodium ions in the surface layer by at least one kind of potassium ions, rubidium ions, and cesium ions.
The glass article pertaining to the third aspect of the present invention is characterized by that the surface thereof which is irradiated with electron rays is modified so that sodium ions are exchanged by potassium ions. It is made from a glass plate composed of SiO2 69˜73%, Al2 O3 0.5˜1.5%, Fe2 O3 0˜0.15%, CaO 7˜14%, MgO 0˜4.5%, Na2 O 12˜16%, K2 O 0˜1.5%, TiO 2 0˜0.1%, SO3 0˜0.5%, and Li2 0.2˜1.5% by weight.
The third aspect of the present invention is based on the following knowledge. The browning caused by electron rays takes place because alkali ions in the outermost layer of glass move inward when the glass is irradiated with electron rays and they change into metallic alkali atoms in a depth of 0.5˜8 μm from the surface. It is known that when there are two or more kinds of alkalis in glass, they prevent browning owing to the mixed alkali effect. Moreover, browning can be prevented more effectively when 0.2˜1.5 wt % of Li2 O is added in addition to Na2 O and K2 O. If the amount of Li2 O is less than 0.2 wt %, browning is not effectively prevented. If the amount of Li2 O is higher than 1.5 wt %, the effect of preventing browning levels off. The weight ratio of Na2 O/(Na2 O+K2 O) should be 0.2˜0.6. Outside this range, the effect of preventing browning is little.
The depth of the layer in which coloring takes place by irradiation with electron rays is determined by the distance to which electron rays penetrate. The depth is expressed by the following formula. (Thomson - Widington Law)
D=V.sup.2 /βd
where D (cm) is a depth in glass to which electron rays penetrate; V (volt) is an accelerating voltage of electron rays; d(g/cm3) is a density of glass; and β is a constant 6.2×1011 volt2.cm2 /g.
Therefore, if the accelerating voltage V (volt) of electron rays is 10 kV, 20 kV, and 30 kV, the electron rays will penetrate to a depth of 0.62 μm, 2.48 μm, and 5.58 μm, respectively. Electron ray was found experimentally to penetrate to a depth of 0.5 to 1.5 μm, 0.75 to 4 μm and 2.0 to 6.5 respectively when the electron ray was irradiated on a surface of soda-lime-silica glass under an accelerating voltage of 10 kV, 20 kV and 30 kV.
These facts suggest that if the composition of the surface layer of a glass molding to which the irradiated electron rays penetrate is adjusted so that the content of Li2 O is 0.2˜1.5 wt % and the ratio of Na2 O/(Na2 O+K2 O) is 0.2˜0.6 the weight glass article is protected from browning by electron rays and has a high strength.
Therefore, the glass molding pertaining to the third aspect of the present invention should have the composition defined as follows: The content of Li2 O in the surface layer deeper than 0.5 μm is 0.2˜1.5 wt %, with the ratio of Na2 O/(Na2 O+K2 O) being 0.2˜0.6.
A glass article like this is produced by the process pertaining to the fourth aspect of the invention. According to the process, a glass plate composed of SiO2 69˜73%, Al2 O3 0.5˜1.5%, Fe2 O3 0˜0.15%, CaO 7˜14%, MgO 0˜4.5%, Na2 O 12˜16%, K2 O 0˜1.5%, TiO 2 0˜0.1%, SO3 0˜0.5%, and Li2 O 0.2˜1.5% by weight, is formed into a desired shape and the glass plate is dipped in a molten salt bath containing potassium ions at 430° to 490° C. for a prescribed period of time, so that sodium ions in the surface layer are partly exchanged by potassium ions.
Better results are obtained when a glass plate of the above-mentioned composition produced by float process is formed into a CRT glass panel and the glass panel is dipped in a molten salt bath containing potassium ions at 430° to 490° C. so that sodium ions in the surface layer of the glass panel are partly exchanged by potassium ions. The ion exchange protects the glass panel from browning by electron rays and produces compression stress in the glass surface, thereby increasing the glass strength.
An advantage of the ion exchange process is that it is possible to control the depth of the surface layer in which the ion exchange takes place by adjusting the period of time during which the glass panel is dipped in the molten salt bath. Thus the dipping time for ion exchange may be properly established according to the accelerating voltage of a CRT.
The above-mentioned glass composition (SiO2 69˜73%, Al2 O3 0.5˜1.5%, Fe2 O3 0˜0.15%, CaO 7˜14%, MgO 0˜4.5%, Na2 O 12˜16%, K2 O 0˜1.5%, TiO 2 0˜0.1%, SO3 0˜0.5%, and Li2 O 0.2˜1.5% by weight) can be obtained using a furnace for the production of soda-lime-silica glass. Therefore, glass article of the present invention can be produced without using a special furnace. This is advantageous in production cost. In addition, if the glass article of the present invention is produced from a glass plate made by float process, it has a smooth surface and needs no polishing after molding.
In the case where the suppression of browning is accomplished by dipping a commercial soda-lime-silica glass plate in a molten salt containing both potassium ions and lithium ions, the glass strength can decrease on account of the exchange of sodium by lithium. This makes it necessary to increase the thickness of the glass plate where the glass plate is used as a vacuum container such as a CRT. Increasing the thickness is disadvantageous in production cost and weight reduction of CRTs.
By contrast, the glass article pertaining to the third and fourth aspects of the present invention has an advantage over the conventional one. The partial exchange of sodium ions by potassium ions renders the glass panel resistant to browning by electron rays on account of the mixed alkali effect. Moreover, it forms a compressed layer of the glass surface and thereby increases the glass strength.
The glass article pertaining to the fourth aspect of the present invention is made of a glass plate composed of SiO2 69˜73%, Al2 O3 0.5˜1.5%, Fe2 O3 0˜0.15%, CaO 7˜14%, MgO 0˜4.5%, Na2 O 12˜16%, K2 O 0˜1.5%, TiO 2 0˜0.1%, SO3 0˜0.5%, and Li2 O 0.2˜1.5% by weight, with the surface thereof modified such that sodium ions therein are partly exchanged by potassium ions. Therefore, it is very little subject to browning when irradiated with electron rays. In addition, it is improved in strength owing to the ion exchange, and therefore, it outperforms the conventional panel with a smaller thickness. It can be obtained using a furnace for the production of soda-lime-silica glass. Therefore, a glass article of the present invention can be produced without using a special furnace. This is advantageous in production cost. In addition, if the glass article of the present invention is produced from a glass plate made by float process, it has a smooth surface and needs no polishing after molding.
The fifth aspect of the present invention is concerned with a process for producing a glass article protected from coloring by electron rays. According to this process, a glass molding formed from soda-lime-silica glass is dipped in a molten salt bath containing potassium ions and at least one kind of calcium ions, barium ions, and strontium ions, so that sodium ions in the surface layer thereof are partly exchanged by potassium ions. The ion exchange is accomplished to such an extent that the molar ratio of Na2 O/(Na2 O+K2 O) becomes 0.4˜0.65 in the surface layer to the depth of maximum range from the surface.
When soda-lime-silica glass is brought into contact with a molten salt bath containing potassium ions and at least one kind of calcium ions, barium ions, and strontium ions, the exchange of sodium ions by potassium ions is suppressed by the action of at least one kind of calcium ions, barium ions, and strontium ions. Thus it is possible to control the molar ratio of Na2 O to the total amount of Na2 O and K2 O to 0.4˜0.65%.
As mentioned above, the depth in glass (maximum range) to which electron rays penetrate is determined by the accelerating voltage of electron rays, and it is known that the depth can be expressed by the formula
D=V.sup.2 /βd
where D (cm) is a depth in glass to which electron rays penetrate; V (volt) is an accelerating voltage of electron rays; d (g/cm3) is a density of glass; and β is a constant 6.2×1011 volt2.cm2 /g.
Therefore, if the accelerating voltage V (volt) of electron rays is 10 kV, 20 kV, and 30 kV, the electron rays will penetrate to a depth of 0.62 μm, 2.48 μm, and 5.58 μm, respectively. Electron ray was found experimentally to penetrate to a depth of 0.5 to 1.5 μm, 0.75 to 4 μm and 2.0 to 6.5 μm respectively when the electron ray was irradiated on a surface of sodium-lime-silica glass under an accelerating voltage of 10 kV, 20 kV and 30 kV.
The period of time for treatment in a molten salt bath should be determined in proportion to the anticipated accelerating voltage of electron rays or the maximum range. Thus it is necessary to carry out the treatment with a salt containing potassium ions and strontium ions, etc. so that the surface layer within the maximum range has a composition defined by the molar ratio of Na2 O to the total amount of Na2 O and K2 O which is 0.4˜0.65.
According to the fifth aspect of the present invention, the molten salt used for the treatment of soda-lime-silica glass should contain 99.90˜99.99 mol % of a salt containing potassium ions. The treatment with the molten salt should preferably be performed at 440° to 480° C. for 0.5 to 4 hours.
The sixth aspect of the present invention is concerned with a process for producing a glass article protected from coloring by electron rays. According to this process, a glass molding formed from soda-lime-silica glass is dipped in a molten salt bath containing potassium ions and lithium ions, so that sodium ions in the surface layer of the glass molding are exchanged by potassium ions and lithium ions. The treated glass article further undergoes heat treatment. The heat treatment may be performed when the article is in a heating process (such as a sealing or baking process) during an assembling process of a CRT. The treatment process may be performed itself. The ion exchange is accomplished to such an extent that the molar ratio of Na2 O/(Na2 O+K2 O) becomes 0.4˜0.65 and that the molar ratio of Li2 O/(total amount of alkalimetal oxides) becomes 0.05˜0.3 in the surface layer almost to the depth of maximum range from the surface.
When a molar ratio for Na2 O/(Na2 O+2O) is 0.4 to 0.65, sodium ions and potassium ions move with smaller diffusion velocity than other molar ratios, whereby alkali ions move so slowly that the formation of the colloids is diminished and the glass article decreases to discolor. An addition of Li2 O with a molar ratio of 0.05 to 0.3 lowers the diffusion velocity, whereby the glass article diminishes further to discolor. A molar ratio of Li2 O of less than 0.05 or more than 0.3 will increase the diffusion velocity and make liable the glass to discolor.
Upon contact with a molten salt containing potassium ions and lithium ions, the surface layer of the soda-lime-silica glass undergoes change in composition. That is, 70˜100% of sodium ions in the surface layer is exchanged by potassium ions and lithium ions. The subsequent heat treatment causes sodium ions and potassium ions to diffuse to the depth of maximum range from the surface. As the result, the composition in the surface layer of that depth has a composition defined by the molar ratio of Na2 O to the total amount of Na2 O and 220 which is 0.4˜0.65 and by the molar ratio of Li2 O to the total amount of alkali-metal oxides which is 0.05˜0.3.
As mentioned above, the depth in glass (maximum range) to which electron rays penetrate is determined by the accelerating voltage of electron rays.
If the accelerating voltage V (volt) of electron rays is 10 kV, 20 kV, and 30 kV, the electron rays will penetrate to a depth of 2.5 μm, 4.5 μm, and 7.5 μm, respectively. Electron ray was found experimentally to penetrate to a depth of 0.5 to 1.5 μm, 0.75 to 4 μm and 2.0 to 6.5 μm respectively when the electron ray was irradiated on a surface of soda-lime-silica glass under an accelerating voltage of 10 kV, 20 kV and 30 kV.
The adequate temperature and time for the treatment should be established according to the anticipated accelerating voltage of electron rays and the conditions of ion exchange, so that the molar ratio of Na2 O to the total amount of Na2 O and K2 O becomes 0.4˜0.65. In general, the ion exchange and heat treatment require a higher temperature and a longer time as the anticipated accelerating voltage of electron rays increases.
According to the sixth aspect of the present invention, potassium nitrate and lithium nitrate are used as the molten salt containing potassium ions and lithium ions. In this case, the molten salt should preferably be kept at 440° to 480° C. and the dipping time should preferably be 0.5 to 4 hours. The heat treatment should be performed at 440° to 480° C. for 1 to 10 hours.
The seventh aspect of the present invention is concerned with a process for producing a glass article protected from coloring by electron rays. According to this process, a glass molding formed from soda-lime-silica glass is dipped in a molten salt bath containing potassium ions, so that sodium ions in the surface layer of the glass molding are exchanged by potassium ions. The treated glass article further undergoes heat treatment. The ion exchange is accomplished to such an extent that the molar ratio of Na2 O/(Na2 O+K2 O) becomes 0.4˜0.65 wt in the surface layer to the depth of maximum range from the surface.
Upon contact with a molten salt containing potassium ions, the surface layer of the soda-lime-silica glass undergoes change in composition. That is, 70˜80% of sodium ions in the surface layer is exchanged by potassium ions, and the surface layer contains both sodium ions and potassium ions. The subsequent heat treatment causes sodium ions and potassium ions to diffuse to the depth of maximum range from the surface. As the result, the composition in the surface layer of that depth has a composition defined by the molar ratio of Na2 O to the total amount of Na2 O and K2 O which is 0.4˜0.65 wt.
As mentioned above, the depth in glass (maximum range) to which electron rays penetrate is determined by the accelerating voltage of electron rays as expressed by the formula
D=V.sup.2 /βd
Therefore, if the accelerating voltage V (volt) of electron rays is 10 kV, 20 kV, and 30 kV, the electron rays will penetrate to a depth of 0.62 μm, 2.48 μm, and 5.58 μm, respectively.
The adequate temperature and time for the treatment should be established according to the anticipated accelerating voltage of electron rays and the conditions of ion exchange, so that the molar ratio of Na2 O to the total amount of Na2 O and K2 O becomes 0.4˜0.65 wt. In general, the ion exchange and heat treatment require a higher temperature and a longer time as the anticipated accelerating voltage of electron rays increases.
According to the seventh aspect of the present invention, potassium nitrate is used as the molten salt containing potassium ions. In this case, the molten salt should preferably be kept at 440° to 480° C. and the dipping time should preferably be 0.5 to 4 hours, and the heat treatment should be performed at 440° to 480° C. for 1 to 10 hours.
According to the fifth, sixth and seventh aspects of the present invention, soda-lime-silica glass is used. The preferred composition of the glass is shown in Table 1.
TABLE 1
______________________________________
Composition of Soda-lime-silica Glass
Component Wt %
______________________________________
SiO.sub.2 50˜ 75
Al.sub.2 O.sub.3
0.5˜ 2.5
MgO 0˜ 4.5
CaO 5.0˜ 14.0
Na.sub.2 O 5.0˜ 16.0
K.sub.2 O 0˜ 2.0
Fe.sub.2 O.sub.3
0˜ 1.0
TiO.sub.2 0˜ 0.5
SO.sub.3 0˜ 0.5
______________________________________
The glass used in the fifth, sixth and seventh aspects of the present invention should have such a composition that the alkali metal oxide accounts for 5 wt % and more, preferably 10 wt % and more, in the glass and sodium oxide accounts for 65 wt % and more, preferably 80 wt % and more, in the alkali metal oxide. With a composition outside this range, the glass article is poor in resistance to coloring by electron rays.
According to the fifth aspect of the present invention, the surface layer of the glass up to a depth of the maximum range is modifies such that the molar ratio of Na2 O to the total amount of Na2 O and K2 O is 0.4˜0.65. The sodium ions and potassium ions present together in the surface layer are less mobile in the glass and hence less liable to form the colloids of alkali-metal atoms. For this reason, the glass article of the present invention is protected from coloring by electron rays.
When the sodium ions, potassium ions and lithium ions present together in the surface layer, the glass article diminishes to discolor further than when two kinds of alkali ions present together therein.
According to the present invention, it is not necessary to use glass of special composition containing a large amount of potassium oxide for the prevention of coloring by electron rays. Therefore, the production of the glass article of the present invention does not need a special furnace and an expensive raw material. The glass article of the present invention is superior in resistance to coloring by electron rays to the conventional glass for picture tubes of color television.
The invention will be more clearly understood with reference to the following examples.
A glass panel, 300 mm wide, 370 mm long, and 50 mm high, having a flat surface as shown in FIG. 1 was produced from a soda-lime-silica glass plate formed by float process, by heating and vacuum forming in combination with pressing. After pretreatment at about 200° C. for about 30 minutes, the glass panel was dipped in a molten salt bath composed of potassium nitrate and lithium nitrate at 460° C. for 2 hours. The content of lithium nitrate in the molten salt bath was 0 mol % in Comparative Example 1, 0.04 mol % in Example 1, 0.15 mol % in Example 2, and 0.4 mol % in Example 3. After dipping, the glass panel was washed.
Table 2 shows the average concentration (wt %) of lithium oxide in the surface layer up to a depth of 10 μm from the surface of the glass panel. Table 2 also shows the molar ratio of Na2 O/(Na2 O+K2 O) in the same surface layer.
The glass panel obtained by the above-mentioned process was irradiated with electron rays for 300 hours using an electron gun (cathode voltage: 21 kV, cathode current: 300 μA, and surface current density: 1.00 μA/cm2). After that, the glass panel was examined for light transmittance at a wavelength of 400 nm. The change of absorbance In (T0 /T) is shown in Table 2. (T0 and T stand for the transmittance of light before and after irradiation with electron rays.)
It is apparently noted from Table 2 that browning in Examples 1 to 3 (in which the concentration of lithium nitrate is 0.04 to 0.4 mol %) was less severe than in Comparative Example 1 (in which lithium nitrate is not contained.) It was found that compressive stress is present in the surface layer of the glass panel, and owing to it the glass panel has an increased strength.
TABLE 2
______________________________________
Ave. conc. Na.sub.2 O/
Lithium (wt %) (Na.sub.2 O +
Change of
nitrate of lithium oxide
K.sub.2 O) absorbance
(mol %) across depth
(molar ratio)
In (T.sub.0 /T)
______________________________________
Compar-
0 0 0.55 0.075
ative
Example
Example
0.04 0.1 0.6 0.055
1
Example
0.15 1.0 0.6 0.035
2
Example
0.4 1.5 0.55 0.025
3
______________________________________
A glass panel, 300 mm wide, 370 mm long, and 50 mm high, having a flat surface as shown in FIG. 1 was produced from a glass plate having the composition as shown in Table 3, by heating and vacuum forming in combination with pressing. After pretreatment at about 200° C. for about 30 minutes, the glass panel was dipped in a molten salt of potassium nitrate at 460° C. for 2 hours. After dipping, the glass panel was washed. For comparison (Comparative Example 3), the same glass panel was produced from glass for color TV picture tubes having the browning-resistant composition as shown in Table 4.
TABLE 3
______________________________________
(wt %)
Example Example
Comparative
Component Example 4 5 6 Example 2
______________________________________
SiO.sub.2 71.31 71.31 71.31 71.31
Al.sub.2 O.sub.3
1.44 1.44 1.44 1.44
Fe.sub.2 O.sub.3
0.094 0.094 0.094 0.094
CaO 8.86 8.86 8.86 8.86
MgO 3.86 3.86 3.86 3.86
Li.sub.2 O
0.2 0.5 1.0 0
Na.sub.2 O + Li.sub.2 O
13.29 13.29 13.29 13.29
K.sub.2 O 0.83 0.83 0.83 0.83
TiO.sub.2 0.03 0.03 0.03 0.03
SO.sub.3 0.21 0.21 0.21 0.21
______________________________________
TABLE 4
______________________________________
Component
Wt %
______________________________________
SiO.sub.2
56.8
Al.sub.2 O.sub.3
2.07
MgO 0.83
CaO 0.23
SrO 9.1
BaO 11.5
ZnO 2.41
Li.sub.2 O
0.41
Na.sub.2 O
7.2
K.sub.2 O
7.23
CeO.sub.2
0.63
TiO.sub.2
0.57
ZrO.sub.2
1.73
Fe.sub.2 O.sub.3
0.035
Sb.sub.2 O.sub.3
0.14
______________________________________
Table 5 shows the ratio by weight of Na2 O/(Na2 O+K2 O) in the same surface layer of the glass panel up to a depth of 2.5 μm from the surface.
A test pieces cut out of the glass panel obtained by the above-mentioned process was irradiated with electron rays for 300 hours using an electron gun (cathode voltage: 20 kV, cathode current: 300 μA, and surface current density: 1.00 μA/cm2). After that, the glass panel was examined for light transmittance at a wavelength of 400 nm. The change of absorbance In (T0 /T) is shown in Table 5. (T0 and T stand for the transmittance of light before and after irradiation with electron rays.)
It is apparently noted from Table 5 that glass panels in Examples 4 to 6 (in which the concentration of lithium oxide is 0.2 to 1.0 wt %) have a good resistance to browning. It was found that compressive stress (80 kg/cm2) is present in the surface layer of the glass panel, and owing to it the glass panel has an increased strength.
TABLE 5
______________________________________
Lithium Ratio by weight
Change of
oxide of Na.sub.2 O/(Na.sub.2 O +
absorbance
(wt %) K.sub.2 O) In (T.sub.0 /T)
______________________________________
Example 4 0.2 0.6 0.20
Example 5 0.5 0.6 0.055
Example 6 1.0 0.55 0.055
Comparative
0 0.55 0.35
Example 2
Comparative
0.41 0.50 0.25
Example 3
______________________________________
A 3-mm thick glass plate formed by float process, having the composition as shown in Table 6 underwent ion exchange. The glass plate was irradiated with electron rays. The coloring caused by the irradiation was evaluated by measuring the change of transmittance.
TABLE 6
______________________________________
Composition of Glass Plate
Component
Wt %
______________________________________
SiO.sub.2
72.92
Al.sub.2 O.sub.3
1.70
MgO 3.83
CaO 7.52
Na.sub.2 O
13.38
K.sub.2 O
0.70
Fe.sub.2 O.sub.3
0.08
SO.sub.3
0.30
______________________________________
The ion exchange was carried out under the following conditions.
Molten salt: Potassium nitrate (purity 99.9%) 99.975 mol % Strontium nitrate 0.025 mol %
Bath temperature: 460° C.
Dipping time: 1 hour
The irradiation of electron rays was carried out under the following conditions.
Accelerating voltage: 10 kV
Surface current density: 2.0 μA/cm2
Irradiation time: 200 hours
The thus obtained test piece was examined for transmittance of light with a wavelength of 400 nm. The results are shown in Table 7.
TABLE 7
______________________________________
Transmittance
Transmittance
Conditions for ion
before after
exchange irradiation irradiation
______________________________________
Example 7
With strontium
90 84
Compara-
Without strontium
90 44
tive
Example 4
Compara-
Picture tube glass
88 56
tive
Example 5
______________________________________
The molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the above-mentioned glass plate was measured using an X-ray microanalyzer (XMA). The results are shown in FIG. 2 (solid line).
In Comparative Example 4, the above-mentioned glass plate was treated with molten potassium nitrate at 460° C. for 1 hour and the treated glass plate was examined for light transmittance (400 nm) before and after irradiation with electron rays. In Comparative Example 5, a commercial glass plate for color picture tubes was examined for light transmittance (400 nm) before and after irradiation with electron rays. The results are shown in Table 7. The molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the plate in Comparative Example 5 was measured. The results are shown in FIG. 2 (broken line). It is noted from Table 7 and FIG. 2 that the glass panel of the present invention decreases much less in transmittance after irradiation with electron rays than that in Comparative Examples 4 and 5.
A 3-mm thick glass plate formed by float process, having the composition as shown in Table 6 underwent ion exchange and subsequent heat treatment. The glass plate was irradiated with electron rays. The coloring caused by the irradiation was evaluated by measuring the change of transmittance.
______________________________________
Molten salt:
Potassium nitrate (purity 99.9%)
99.9 wt %
Lithium nitrate 0.1 wt %
Bath temperature:
460° C.
Dipping time:
3 hour
Heat treatment:
at 460° C. for 4 hours.
______________________________________
The irradiation of electron rays was carried out under the following conditions.
Accelerating voltage: 10 kV
Surface current density: 35 μA/cm2
Irradiation time: 20 hours
The thus obtained test piece was examined for transmittance of light with a wavelength of 400 nm. The results are shown in Table 8.
TABLE 8
______________________________________
Heat Transmittance
Transmittance
Ion treat- before after
exchange ment irradiation irradiation
______________________________________
Example 8
KNO.sub.3
yes 90 75
Yes
LiNO.sub.3
Compara-
yes no 90 35
tive
Example 6
Compara-
Picture tube glass
88 50
tive
Example 7
______________________________________
The molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the above-mentioned glass plate was measured using an X-ray microanalyzer (XMA). The results are shown in FIG. 3 (solid line). FIG. 4 shows the molar ratio of Li2 O/(Li2 O+Na2 O+K2 O) in the Example 8.
In Comparative Example 6, the above-mentioned glass plate underwent ion exchange but did not undergo heat treatment. In Comparative Example 7, a commercial glass plate for color picture tubes had the composition as shown in Table 4. These glass plates in Comparative Example 6 and Comparative Example 7 were examined for light transmittance (400 nm) before and after irradiation with electron rays. The results are shown in Table 8. The molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the plate in Comparative Example 6 was measured. The results are shown in FIG. 3 (broken line). It is noted from Table 8 and FIG. 3 that the glass panel of the present invention decreases much less in transmittance after irradiation with electron rays than that in Comparative Examples 6 and 7.
A 3-mm thick glass plate formed by float process, having the composition as shown in Table 6 underwent ion exchange and subsequent heat treatment. The glass plate was irradiated with electron rays. The coloring caused by the irradiation was evaluated by measuring the change of transmittance. The ion exchange was carried out under the following conditions.
Molten salt: Potassium nitrate (purity 99.9%)
Bath temperature: 460° C.
Dipping time: 2 hour
Heat treatment: at 460° C. for 4 hours.
The irradiation of electron rays was carried out under the following conditions.
Accelerating voltage: 10 kV
Surface current density: 2.0 μA/cm2
Irradiation time: 200 hours
The thus obtained test piece was examined for transmittance of light with a wavelength of 400 nm. The results are shown in Table 9.
TABLE 9
______________________________________
Transmittance
Transmittance
Ion Heat before after
exchange treatment
irradiation irradiation
______________________________________
Example
yes yes 90 84
Compar-
yes no 90 42
ative
Example
6
Compar-
Picture tube glass
88 56
ative
Example
9
______________________________________
The molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the above-mentioned glass plate was measured using an X-ray microanalyzer (XMA). The results are almost same as shown in FIG. 3 (solid line)
In Comparative Example 8, the above-mentioned glass underwent ion exchange but did not undergo heat treatment. In Comparative Example 9, a commercial glass plate for color picture tubes had the composition as shown in Table 4. These glass plates in Comparative Example 8 and Comparative Example 9 were examined for light transmittance (400 nm) before and after irradiation with electron rays. The results are shown in Table 9. The molar ratio of Na2 O/(Na2 O+K2 O) in the surface layer of the plate in Comparative Example 8 was measured. The results are almost same as shown in FIG. 3 (broken line). It is noted from Table 9 and FIG. 3 that the glass panel of the present invention decreases much less in transmittance after irradiation with electron rays than that in Comparative Examples 8 and 9.
Claims (4)
1. A glass article protected from coloring by electron rays, comprising:
soda-lime-silica a glass having a surface to which electron rays are irradiated, said glass being produced by a float process with molten tin and composed of 69-73% by weight of SiO2, 0.5-1.5% by weight of Al2 O3, 0-0.15% by weight of Fe2 O3, 7-14% by weight of CaO, 0-4.5% by weight of MgO, 12-16% by weight of Na2 O, 0-1.5% by weight of K2 O, 0-0.1% by weight of TiO2, and 0-0.5% by weight of SO3, said surface being prevented from contact with the molten tin during glass production, and
lithium ions and at least one member selected from the group consisting of potassium ions, rubidium ions and cesium ions substituted for sodium ions around the surface of the glass, average content of Li2 O for a depth of 10 micra from the surface of the glass being 0.1-3 wt %.
2. A glass article as claimed in claim 1, wherein at least one of potassium ions, rubidium ions and cesium ions penetrates to a depth of 5-20 micra from the surface of the glass.
3. A glass article protected from coloring by electron rays, comprising:
a glass article having a surface to which electron rays are irradiated, said glass article being composed of 69-73% by weight of SiO2, 0.5-1.5% by weight of Al2 O3, 0-0.15% by weight of Fe2 O3, 7-14% by weight of CaO, 0-4.5% by weight of MgO, 12-16% by weight of Na2 O, 0-1.5% by weight of K2 O, 0-0.1% by weight of TiO2, 0-0.5% by weight of SO3, and 0.2-1.5% by weight of Li2 O, and
potassium ions substituted for sodium ions around the surface of the glass, and weight ratio of Na2 O/(Na2 O+K2 O) being 0.2-0.6 for a depth of 0.5 micron or more from the surface of the glass.
4. A glass article protected from coloring by electron rays, comprising:
a glass article having a surface to which electron rays are irradiated, said glass article being composed of 69-73% by weight of SiO2, 0.5-1.5% by weight of Al2 O3, 0-0.15% by weight of Fe2 O3, 7-14% by weight of CaO, 0-4.5% by weight of MgO, 12-16% by weight of Na2 O, 0-1.5% by weight of K2 O, 0-0.1% by weight of TiO2, 0-0.5% by weight of SO3, and 0.2-1.5% by weight of Li2 O, and
potassium ions partly substituted for sodium ions around the surface of the glass by dipping the glass article in a molten salt containing potassium ions at 430°-490° C. for a prescribed period of time.
Applications Claiming Priority (8)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2321687A JPH07108797B2 (en) | 1987-02-03 | 1987-02-03 | Glass panel irradiated with electron beam and method for manufacturing the same |
| JP62-23216 | 1987-02-03 | ||
| JP62-24381 | 1987-02-04 | ||
| JP2438187A JPH07102981B2 (en) | 1987-02-04 | 1987-02-04 | Glass panel irradiated with electron beam and method for manufacturing the same |
| JP62241591A JPH06104580B2 (en) | 1987-09-25 | 1987-09-25 | Method for producing glass article for preventing electron beam coloring |
| JP62241592A JPH06104581B2 (en) | 1987-09-25 | 1987-09-25 | Method for producing glass article in which coloring by electron beam is prevented |
| JP62-241591 | 1987-09-25 | ||
| JP62-241592 | 1987-09-25 |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/384,126 Division US5057134A (en) | 1987-02-03 | 1989-07-24 | Process for producing a glass article protected from coloring by electron rays |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US4897371A true US4897371A (en) | 1990-01-30 |
Family
ID=27457917
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/146,449 Expired - Lifetime US4897371A (en) | 1987-02-03 | 1988-01-21 | Glass article protected from coloring by electron rays and method of using |
| US07/384,126 Expired - Lifetime US5057134A (en) | 1987-02-03 | 1989-07-24 | Process for producing a glass article protected from coloring by electron rays |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US07/384,126 Expired - Lifetime US5057134A (en) | 1987-02-03 | 1989-07-24 | Process for producing a glass article protected from coloring by electron rays |
Country Status (3)
| Country | Link |
|---|---|
| US (2) | US4897371A (en) |
| FR (1) | FR2610317B1 (en) |
| GB (3) | GB2200627B (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5215944A (en) * | 1991-07-29 | 1993-06-01 | Ppg Industries, Inc. | X-ray absorbing glass compositions |
| US5296294A (en) * | 1987-02-03 | 1994-03-22 | Nippon Sheet Glass Co., Ltd. | Glass panel resistant to coloring when irradiated with electron rays |
| EP1125900A1 (en) * | 2000-02-10 | 2001-08-22 | Sony Corporation | Glass panel for cathode ray tube, cathode ray tube employing this glass panel and method for producing cathode ray tube |
| EP1153410A1 (en) * | 1998-10-28 | 2001-11-14 | International Lead Zinc Research Organization | Cathode ray tubes with reduced browning properties |
| EP1241144A1 (en) * | 2001-03-16 | 2002-09-18 | HERO-GLAS Veredelungs GmbH | Laminated safety glass and its process of prodction |
| US6607999B2 (en) | 2000-02-17 | 2003-08-19 | Hoya Corporation | Glass for cathode-ray tube, strengthened glass, method for the production thereof and use thereof |
| US20060032842A1 (en) * | 2003-02-04 | 2006-02-16 | Kuniaki Hiromatsu | Method for removing foreign matter on glass substrate surface |
| US9206079B2 (en) | 2011-09-29 | 2015-12-08 | Central Glass Company, Limited | Chemically strengthened glass plate and method for manufacturing same |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0651423B1 (en) * | 1990-09-13 | 1998-03-04 | Nippon Sheet Glass Co., Ltd. | Glass front-panel and cathode ray tube incorporating the same |
| US5357165A (en) * | 1990-09-13 | 1994-10-18 | Nippon Sheet Glass Co., Ltd. | Glass front-panel |
| US5252112A (en) * | 1990-09-13 | 1993-10-12 | Nippon Sheet Glass Co., Ltd. | Method of producing a glass front-panel protected from coloring by electron rays |
| DE69121497T2 (en) * | 1990-09-13 | 1997-02-20 | Nippon Sheet Glass Co Ltd | Glass faceplate for cathode ray tube and manufacturing process |
| DE69317382T2 (en) * | 1992-12-14 | 1998-08-13 | Nippon Sheet Glass Co Ltd | Glass pane resistant to coloring by irradiation with electron beams |
| DE19616679C1 (en) * | 1996-04-26 | 1997-05-07 | Schott Glaswerke | Chemically toughened alumino-silicate glass production |
| AU736751B2 (en) | 1996-12-26 | 2001-08-02 | Canon Kabushiki Kaisha | Electron source substrate and electron source and image-forming apparatus using such substrate as well as method of manufacturing the same |
| FR2765569B3 (en) * | 1997-07-01 | 1999-07-16 | Saint Gobain Vitrage | GLASS COMPOSITION OF THE SILICO-SODO-CALCIUM TYPE |
| FR2768857B1 (en) * | 1997-09-23 | 1999-12-03 | Thomson Tubes Electroniques | METHOD FOR PRODUCING A VISUALIZATION PANEL COMPRISING A SLAB WITH IMPROVED DIMENSIONAL STABILITY |
| GB2329382A (en) * | 1997-09-23 | 1999-03-24 | Glaverbel | Chemical treatment of vitreous material |
| JP2012214356A (en) * | 2010-12-29 | 2012-11-08 | Avanstrate Inc | Cover glass and method for producing the same |
| JP6233312B2 (en) * | 2012-09-14 | 2017-11-22 | 旭硝子株式会社 | Chemically strengthened glass, chemically strengthened glass, and method for producing chemically strengthened glass |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1248481A (en) * | 1968-03-04 | 1971-10-06 | Saint Gobain | A method of increasing the mechanical strength of a glass object |
| US3790430A (en) * | 1961-06-12 | 1974-02-05 | Corning Glass Works | Alkali aluminosilicate glass article having an ion-exchanged surface layer |
| JPS50105705A (en) * | 1974-01-29 | 1975-08-20 | ||
| US4192689A (en) * | 1978-05-30 | 1980-03-11 | Ppg Industries, Inc. | Ion exchange strengthening of soda-lime-silica glass |
| US4403043A (en) * | 1981-08-31 | 1983-09-06 | Hoya Corporation | Glass for photoetching mask |
| GB2171990A (en) * | 1985-03-08 | 1986-09-10 | Central Glass Co Ltd | Method of strengthening glass article formed of float glass by ion exchange and strengthened glass article |
| JPS62153148A (en) * | 1985-12-25 | 1987-07-08 | Nippon Sheet Glass Co Ltd | Glass panel to be irradiated with electron ray and rpoduction thereof |
Family Cites Families (20)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL298724A (en) * | 1962-10-04 | |||
| US3357876A (en) * | 1965-01-19 | 1967-12-12 | Pittsburgh Plate Glass Co | Method of strengthening a glass article by ion exchange |
| NL135450C (en) * | 1964-01-31 | 1900-01-01 | ||
| US3433611A (en) * | 1965-09-09 | 1969-03-18 | Ppg Industries Inc | Strengthening glass by multiple alkali ion exchange |
| US3844754A (en) * | 1966-02-23 | 1974-10-29 | Owens Illinois Inc | Process of ion exchange of glass |
| US3637453A (en) * | 1966-06-17 | 1972-01-25 | Owens Illinois Inc | Glass-ceramic articles having an integral compressive stress surface layer |
| DD69678A (en) * | 1967-04-28 | |||
| US3607172A (en) * | 1968-11-01 | 1971-09-21 | Brockway Glass Co Inc | Tripotassium phosphate treatment for strengthening glass |
| GB1266257A (en) * | 1969-03-27 | 1972-03-08 | ||
| US3751238A (en) * | 1970-02-25 | 1973-08-07 | Corning Glass Works | Method of chemically strengthening a silicate article containing soda |
| JPS5417765B1 (en) * | 1971-04-26 | 1979-07-03 | ||
| DE2526804B2 (en) * | 1975-06-16 | 1979-06-07 | Jenaer Glaswerk Schott & Gen., 6500 Mainz | Procedure for changing the |
| CA1092358A (en) * | 1977-08-18 | 1980-12-30 | Leon Levene | Method of strengthening glass articles with potassium fluoride-metal acetate |
| US4156755A (en) * | 1978-04-19 | 1979-05-29 | Ppg Industries, Inc. | Lithium containing ion exchange strengthened glass |
| US4273832A (en) * | 1978-08-04 | 1981-06-16 | Brockway Glass Company, Inc. | Glass article strengthened by ion exchange substitution |
| US4218230A (en) * | 1978-08-04 | 1980-08-19 | Brockway Glass Company, Inc. | Method of glass strengthening by ion exchange |
| JPS605538B2 (en) * | 1979-11-27 | 1985-02-12 | 日本板硝子株式会社 | Cesium-containing optical glass |
| US4455160A (en) * | 1982-12-20 | 1984-06-19 | Corning Glass Works | Transparent glass-ceramics especially suitable for use as stove windows |
| JPH0818850B2 (en) * | 1986-09-05 | 1996-02-28 | セントラル硝子株式会社 | Chemically tempered glass |
| US4872896A (en) * | 1988-05-27 | 1989-10-10 | Alfred University | Process for strengthening glass |
-
1988
- 1988-01-21 US US07/146,449 patent/US4897371A/en not_active Expired - Lifetime
- 1988-02-02 GB GB8802222A patent/GB2200627B/en not_active Expired - Fee Related
- 1988-02-02 FR FR888801191A patent/FR2610317B1/en not_active Expired - Fee Related
-
1989
- 1989-07-24 US US07/384,126 patent/US5057134A/en not_active Expired - Lifetime
-
1990
- 1990-09-13 GB GB9020022A patent/GB2236316B/en not_active Expired - Fee Related
- 1990-09-13 GB GB9020023A patent/GB2236317B/en not_active Expired - Fee Related
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3790430A (en) * | 1961-06-12 | 1974-02-05 | Corning Glass Works | Alkali aluminosilicate glass article having an ion-exchanged surface layer |
| GB1248481A (en) * | 1968-03-04 | 1971-10-06 | Saint Gobain | A method of increasing the mechanical strength of a glass object |
| JPS50105705A (en) * | 1974-01-29 | 1975-08-20 | ||
| US4192689A (en) * | 1978-05-30 | 1980-03-11 | Ppg Industries, Inc. | Ion exchange strengthening of soda-lime-silica glass |
| US4403043A (en) * | 1981-08-31 | 1983-09-06 | Hoya Corporation | Glass for photoetching mask |
| GB2171990A (en) * | 1985-03-08 | 1986-09-10 | Central Glass Co Ltd | Method of strengthening glass article formed of float glass by ion exchange and strengthened glass article |
| JPS62153148A (en) * | 1985-12-25 | 1987-07-08 | Nippon Sheet Glass Co Ltd | Glass panel to be irradiated with electron ray and rpoduction thereof |
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5296294A (en) * | 1987-02-03 | 1994-03-22 | Nippon Sheet Glass Co., Ltd. | Glass panel resistant to coloring when irradiated with electron rays |
| US5215944A (en) * | 1991-07-29 | 1993-06-01 | Ppg Industries, Inc. | X-ray absorbing glass compositions |
| EP1153410A1 (en) * | 1998-10-28 | 2001-11-14 | International Lead Zinc Research Organization | Cathode ray tubes with reduced browning properties |
| EP1153410A4 (en) * | 1998-10-28 | 2003-01-22 | Int Lead Zinc Res | Cathode ray tubes with reduced browning properties |
| EP1125900A1 (en) * | 2000-02-10 | 2001-08-22 | Sony Corporation | Glass panel for cathode ray tube, cathode ray tube employing this glass panel and method for producing cathode ray tube |
| US6607999B2 (en) | 2000-02-17 | 2003-08-19 | Hoya Corporation | Glass for cathode-ray tube, strengthened glass, method for the production thereof and use thereof |
| EP1241144A1 (en) * | 2001-03-16 | 2002-09-18 | HERO-GLAS Veredelungs GmbH | Laminated safety glass and its process of prodction |
| US20060032842A1 (en) * | 2003-02-04 | 2006-02-16 | Kuniaki Hiromatsu | Method for removing foreign matter on glass substrate surface |
| US7767929B2 (en) * | 2003-02-04 | 2010-08-03 | Asahi Glass Company, Limited | Method for removing foreign matter on glass substrate surface |
| US9206079B2 (en) | 2011-09-29 | 2015-12-08 | Central Glass Company, Limited | Chemically strengthened glass plate and method for manufacturing same |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2610317B1 (en) | 1992-11-27 |
| GB9020022D0 (en) | 1990-10-24 |
| GB8802222D0 (en) | 1988-03-02 |
| GB2236316B (en) | 1991-12-04 |
| GB2236316A (en) | 1991-04-03 |
| GB9020023D0 (en) | 1990-10-24 |
| GB2200627A (en) | 1988-08-10 |
| GB2236317B (en) | 1991-09-25 |
| FR2610317A1 (en) | 1988-08-05 |
| GB2236317A (en) | 1991-04-03 |
| GB2200627B (en) | 1991-11-20 |
| US5057134A (en) | 1991-10-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4897371A (en) | Glass article protected from coloring by electron rays and method of using | |
| US4390637A (en) | X-Ray absorbing glass for a color cathode ray tube having a controlled chromaticity value and a selective light absorption | |
| US4015966A (en) | Manufacture of X-ray absorbing glass composition by a float glass process | |
| US4065697A (en) | Cathode-ray tube | |
| US6548434B2 (en) | Palely colored glass having high transmittance and method for producing the same | |
| US4277286A (en) | Lead-free glasses of high x-ray absorption for cathode ray tubes | |
| US5296294A (en) | Glass panel resistant to coloring when irradiated with electron rays | |
| US5888917A (en) | Glass substrate for plasma display panel | |
| US3143683A (en) | Television tube with improved optical filter | |
| US4337410A (en) | Cathode-ray tube face-plate | |
| US3805107A (en) | Faceplate for television picture tube | |
| US3819972A (en) | Novel glass compositions and cathode-ray tubes made therefrom | |
| US4737475A (en) | Arsenic-free lead silicate vacuum tube glass | |
| US2901366A (en) | Glass composition | |
| US4179638A (en) | Cathode ray tube panel | |
| JP2548423B2 (en) | Glass panel | |
| US5215944A (en) | X-ray absorbing glass compositions | |
| US4786619A (en) | Television face plates resistant to browning | |
| US4680503A (en) | Glass composition suitable for use in a fluorescent lamp and in a cathode-ray tube, fluorescent lamp and cathode-ray tube manufactured using this glass composition | |
| US2669807A (en) | Glass composition | |
| JPH0613419B2 (en) | Glass panel irradiated with electron beam and method for manufacturing the same | |
| US4677081A (en) | Arsenic-free lead silicate vacuum tube glass | |
| US3627549A (en) | Barium silicate glass for television display cathode-ray tubes | |
| JPH07102981B2 (en) | Glass panel irradiated with electron beam and method for manufacturing the same | |
| US6103649A (en) | High X-ray absorbing panel glass for cathode ray tubes |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| AS | Assignment |
Owner name: NIPPON SHEET GLASS CO., LTD., 8 DOSHOMACHI 4-CHOME Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:SUZUKI, KOUICHI;SHIBAOKA, KAZUO;REEL/FRAME:004822/0415 Effective date: 19880109 Owner name: NIPPON SHEET GLASS CO., LTD., A CORP. OF JAPAN,JAP Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SUZUKI, KOUICHI;SHIBAOKA, KAZUO;REEL/FRAME:004822/0415 Effective date: 19880109 |
|
| STCF | Information on status: patent grant |
Free format text: PATENTED CASE |
|
| FEPP | Fee payment procedure |
Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
| CC | Certificate of correction | ||
| FPAY | Fee payment |
Year of fee payment: 4 |
|
| FPAY | Fee payment |
Year of fee payment: 8 |
|
| FPAY | Fee payment |
Year of fee payment: 12 |